At 11.13 -0700 1999-05-25, John Cowan wrote:
>I find this document distressing, not because of its views on UTF-7,
>but because of its views on Unicode language tags. It nowhere
>takes account of the fact that language tags are not yet part of
>Unicode or ISO 10646, and it recommends their use only in
>multi-language documents, a position which cannot be justified
>from the UTR.

The language tags are specified in RFC 2482, and the IESG have a note
in the beginning of that RFC stating:

IESG Note:

This document has been accepted by ISO/IEC JTC1/SC2/WG2 in meeting
#34 to be submitted as a recommendation from WG2 for inclusion in
Plane 14 in part 2 of ISO/IEC 10646.

I.e. it is correct that it is not part of the standards, but it was
accepted by the IESG and the Unicode Consortium to publish the RFC in
question with the above note. The RFC will be updated when ISO
updates 10646.

This is the reason why we have what we call "IESG notes". If it is
the case that the state of language codes is described differently in
the document you refer to, please let the author know of the errors
you think the author have done, and refer to the note in the RFC.